By Alistair Johnston
There is a direct correlation between soil volume and the mature size and optimum health a tree will achieve. To reach a 200-mm (7.8-in.) stem diameter (measured at 1.4 m [4.5 ft from grade]), a tree requires approximately 11 m3 (388 cf) of soil. To reach maturity or 0.5 m (1.6 ft) in diameter, a tree requires approximately 34 m3 (1200 cf) of soil.
Due to the expanse of hard surfaces and a network of underground utilities, it is often a major challenge to provide enough space for 34 m3 (1200 cf) of soil. Three innovative methods are now being implemented to improve soil volumes and reduce heavy soil compaction. The use of CU-Structural Soil Urban Tree Planting Mix (a soil and aggregate mix), soil trenches (suspended concrete slab over topsoil-filled trench) and Silva Cells (modular suspended pavement system) allow for the creation of soil volume, while providing support for surface paving within the root growth area. Each method has its appropriate use, but they have all demonstrated the ability to improve the environment in which root development may occur.
Read the full article: Growing Trees in the Urban Jungle